In formwork technology difference is made between a first formwork and a closing formwork. A first formwork is a formwork which is mounted first. Subsequent to this the closing formwork is mounted opposite to the first formwork. Concrete is cast in the interstitial space between the first formwork and the closing formwork. By curing the concrete a wall is produced.
Generally one or both ends of an anchor rod have threads into which screw nuts are inserted as an anchor fixation. The central area of such an anchor rod to which, during concrete casting, concrete may be adjacent advantageously either has a smooth surface or at least will be encased by a bushing having a smooth surface. Otherwise the thread of an anchor rod would be set in concrete. The anchor rod then may not be easily pulled out of the cured concrete.
The maximum effective length of the anchor rod and hence the strength (thickness) of the wall to be concrete cast is regularly defined by the length of the central range of the anchor rod having a smooth surface. At the same time pressure exerted onto the formwork facing by liquid concrete during casting will be dissipated via the screw nuts. The anchor rods thereby will be tensile-strained.
Between the formwork facings spacers may be inserted into the volume of the wall to be cast which may absorb the compressive forces emerging during casting, thereby assuring these compressive forces not to affect the wall thickness in an undesirable manner, i.e. reducing the wall thickness. Alternatively or additionally the locking devices may also be mounted onto the wall formworks so that the latter may also be able to absorb compressive forces.
From the document WO 2008/089737 A1 an anchoring system having two locking devices and one anchor rod for a wall formwork having first and a second formwork elements is known. The anchor rod on each of its both ends has a thread which is inserted into the screw nut elements of the locking devices. Each locking device comprises a calotte plate which is mounted to a back side of a wall formwork by way of mounting means. The anchor system may hence absorb both tensile and compressive forces.